The chances are that your friend was buried or cremated in the parish where she was last living, or, if she had not lived there for very long, in the parish where she lived previously.
Such a place may or may not be where she died, of course, and her death will have been registered at the register office applicable to the place of her death. As long as she died no later than December 2003, and in England, I may very well be able to find out for you where her death was registered. But you would need to tell me her full name (married name if she was married). If her name is a fairly commonly occurring name it would help also to know her birthday, or at least the year of her birth.